This invention generally relates to devices and methods for detecting a rotation angle. More particularly, the present invention relates to a combined coil and a pointer utilizing the combined coil for detecting a rotation angle and a related method.
A conventional device for detecting a rotation angle may be exemplified by a combined coil disclosed in Japanese laid-open patent publications Nos. 8-30374 and 8-286810. The inventors of these patent publications belong to the same company as the inventors of the present invention. The conventional combined coil will be briefly explained below.
As shown in FIG. 2, a conventional combined coil 95 includes two magnetic cores 93 and 94 arranged side by side. A coordinate detection coil 90 is wound around both magnetic cores 93 and 94 while a control coil 91 is wound around only magnetic core 93. Control coil 91 encircles part of the magnetic flux generated by coordinate detection coil 90. Thus, a rotation angle can be detected by switch-controlling control coil 91 and changing the distribution of the magnetic flux that pass through coordinate detection coil 90.
This conventional combined coil is a solid construction where both control coil 91 and coordinate detection coil 90 must be rotated simultaneously for control coil 91 to assume different rotation angles. In other words, control coil 91 alone cannot be rotated around a center of coordinate detection coil 90 without rotating coordinate detection coil 90.
The conventional combined coil of solid construction is suitable for a pen-shaped pointer, such as an electric pen or a stylus pen, because it can be easily loaded within a narrow outer housing. A tip of the electric pen, located on the line extending from the center axis of coordinate detection coil 90, contacts a tablet surface to indicate the coordinate value. An operator may then utilize the tip as an axis of rotation. Thus, it is easy for the operator to rotate the whole electric pen about the tip so that the control coil assumes different rotation angles around the center of the coordinate detection coil.
On the other hand, a pack-shaped pointer, such as a cursor, a cordless mouse or the like (hereinafter referred as a cursor), contains a relatively wide outer housing. Therefore, it does not have to utilize the conventional solid construction. Furthermore, a pack-shaped pointer does not have a structure like the tip of the electric pen that contacts the tablet surface to indicate the coordinate value. Consequently, it is not easy for an operator to rotate the whole pack-shaped pointer around a certain coordinate.
Therefore, it is desirable to rotate a combined coil without rotating the whole pack-shaped pointer that contains the combine coil. However, a pack-shaped pointer provided with a mechanism to rotate the combined coil creates a new problem to solve. Because the signal lines from the coordinate detection coil as well as those from the control coil should be connected to a circuit that is fixed within the pointer, a structure and a related method are needed to prevent the signal lines from twisting. Otherwise, the signal lines may eventually disconnect from the circuit or a rotation angle will be limited to a narrow range to avoid the disconnection.
Accordingly, the present invention is directed to a combined coil and a pointer utilizing the combined coil for detecting a rotation angle and a related method that obviate one or more of the limitations and disadvantages of prior art devices for detecting a rotation angle. The advantages and purposes of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages and purposes of the invention will be realized and attained by the elements and combinations particularly pointed out in the appended claims.
To attain the advantages and in accordance with the purposes of the invention, as embodied and broadly described herein, the invention is directed to a device for detecting a rotation angle. The device includes a first coil, a second coil, and a twist prevention mechanism. The first coil detects a coordinate value. The second coil detects the rotation angle. The second coil includes signal lines extending therefrom. The second coil is rotatable around a center of the first coil without rotating the first coil. The twist prevention mechanism prevents the signal lines from twisting.
In another aspect, the invention is directed to a pointer for detecting a rotation angle. The pointer includes a first coil, a second coil, a circuit, and a twist prevention mechanism. The first coil detects a coordinate value of the pointer. The second coil detects the rotation angle. The second coil includes signal lines extending therefrom. The second coil is rotatable around a center of the first coil without rotating the first coil. The circuit is connected to the signal lines. The twist prevention mechanism prevents the signal lines from twisting.
In yet another aspect, the invention is directed to a method for detecting a rotation angle without twisting signal lines. The signal lines include a first and second ends. The method includes the steps of: providing a first coil to detect a coordinate value; connecting a second coil to the first end of the signal lines to detect the rotation angle; connecting a circuit to the second end of the signal lines; rotating the second coil around a center of the first coil without rotating the first coil; and causing the first end of the signal lines to always face the circuit.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.